I'm not familiar with such an effect (one might exist, but I'm not
familiar with it). There are a couple of work-arounds I can think of.
The simplest one would be to have a duplicate object that is in front
and apply an entrance effect (such as Appear) to that. When you play the
slideshow, no one would know that you had two objects.
You'll have to fake it by placing a duplicated object "in the front" then
giving it an Enter effect like fade or appear. Depending on where it "moves"
you may have to give the original object an Exit or Emphasis effect.